Antonie van Leeuwenhoek

He was a Dutch merchant and amateur scientist. He was probably the first person to observe live micro-organisms under magnifying lenses. He made a series of drawings of what he called as 'animalcules' i.e. small animals. He observed these by looking through his single-lens microscope at rainwater, his own feces and scrapings from his teeth. He made the drawings shown below.